Hemispherical Liners Research Articles

Formation of an Explosively Formed Penetrator Warhead Using a Step-Shaped Charge

In this study, the formation mechanism of an explosively formed penetrator (EFP) with tail fins was analyzed. Through static denotation and dynamic flight tests, the feasibility of using a step-shaped liner during the formation of an EFP with tail fins was verified. The influences of the step depth, h, and the step angle, Φ, on the flight stability were then explored. Based on the consistency between the numerical simulation and experimental results, the influences of the step-shaped liner’s spherical arc radius, number of steps, and wall thickness on the formation and flight stability of an EFP with tail fins were further studied. The results showed that a T2 copper step-shaped liner performed better than a H90 brass liner. Compared with a hemispherical liner with an equal wall thickness, the step-shaped liners resulted in EFPs with initial angular velocities and relatively better flight stability. Moreover, a greater initial angular velocity led to a higher EFP landing accuracy.

Energy Release Study of Reaction Fragment in Dynamic Loads

Al-W-KClO3 is a kind of metastable reactive composite material, which belongs to multi-functional energetic structure material. Its energy release characteristic under dynamic loading was studied in this paper. The Al-W-KClO3 powder of different components was first pressed to study their forming ability. The Al-W-KClO3 powders of four different molar ratios were moulded into approximate hemispherical liner on a basis of fine formability. The reaction energy releasing characteristics of reactive fragments were researched under the dynamic loads. The steel target was penetrated by the four kinds of reactive fragments, respectively in a high detonation velocitiy and low one, then the effect of penetrating was also analyzed. The result showed that the energetic materials of Al-W-KClO3 could maintain a fine formability and a fine reaction-energy release property at certain ratio of constituents.

Experimental and numerical investigation of zirconium jet performance with different liner shapes design

This paper studies the shaped charge jet performance in terms of different liner shapes including conical, bell, hemispherical and bi-conical liners. The critical angles and the relevant flow velocities for the zirconium liner material were calculated analytically and numerically using Autodyn hydro-code. The relationship between the critical collapse angle and the flow velocity was determined for the conditions of jet formation and coherency. Penetration tests according to the standard testing procedures of API-RP34 (Section-II) were performed to validate the numerical predictions of the jet performance of the studied liners. It was found that the four shaped charge liners all produced coherent jets with different performances. The penetration depth of the shaped charges with the bell and the bi-conical liner shapes increased by 10.3% and 22%, respectively, while the crater diameter of shaped charge with hemispherical liner increased by 85% representing the formation of an explosively-formed-projectile (EFP), when they are compared with the corresponding jet characteristics of a conical liner shaped charge.

Computational and Experimental Study of Operation of Shaped Charges with Hemispherical Liners of Degressive Thickness

Operation of shaped charges with copper hemispherical liners of degressive (decreasing from top to bottom) thickness is experimentally studied. The velocity of the head of generated shaped-charge jets is determined along with how deep they penetrate a type-setting target made of steel disks and the sizes of holes made in the disks. The experimental data on an increase in the velocity and a decrease in the mass of the heads of shaped-charge jets, which occur with an increase in the difference in the thicknesses of the hemispherical liner at the apex and at the base are in good agreement with the results of numerical simulation carried out within the framework of a two-dimensional axisymmetric problem of continuous mechanics. According to the experimental results, the effect of technological manufacturing errors on the operation of these charges becomes stronger, which eliminates or significantly limits the increase in the penetrating action. In one of the versions of liners of degressive thickness, the depth of penetration of a target, which is average in two tests, increases by 7.5% as compared to the liner of constant thickness.

О возможности использования формируемых взрывом компактных поражающих элементов для пробития подводных преград

The paper considers the possibility of using compact projectiles formed by an explosion to break through strong steel barriers of finite thickness protected by a layer of water. There is no problem in penetrating such barriers by high-gradient and high-speed shaped-charge jet of a small diameter formed by shaped charges with ‘high’ conical liners, however, the diameter of the through hole formed in the steel barrier is fairly small and does not meet the defeat criteria for corresponding barriers. To increase the diameter of a through hole in a steel barrier, shaped charges with ‘low’ conical or flat hemispherical liners (in the form of a meniscus) forming compact projectiles can be used, but the movement of such ‘shock cores’ in the water layer is sharply slowed down, up to a complete stop even before interacting with the main steel barrier. The purpose of the paper is to substantiate the possibilities of eliminating this disadvantage when using compact projectiles. Based on theoretical and experimental studies, the paper offers a technical solution related to the known fact of the formation of a cavern (gas cavity) during the movement of a shaped-charge jet in water, expanding as the jet penetrates in the radial direction. In this case, if a known tandem scheme of shaped charges placed one after the other along the axis of the explosive device is used, the first shaped charge, often called pre-charge, will penetrate the body in the head part of the explosive device to the water layer, then form in the latter a cavern up to the main penetrable barrier and the second shaped charge, often referred to as the primary, will form a compact projectile moving to penetrable barrier in the cavity formed by the penetration of shaped-precharge jet in the water. At the same time, due to selecting the necessary delay time between the pre-charge and main charge explosions as well as the design parameters of the pre-charge, the size of the expanding cavity must exceed the size of the compact projectile, excluding its interaction with water up to the approach to the penetrable steel barrier.

On the Penetration Capability of Shaped Charges with Conical and Hemispherical Liners

This paper presents a computational comparison of the penetration capability of two shaped charges—with conical and hemispherical (degressive thickness) liners. It is shown that close values of the penetration capability of the charges are provided only in the ideal case of strictly axisymmetric motion of shaped-charge jets.

Numerical Simulation on Conical Shaped Charge with Copper Liner in Several Typical Shapes

Jet formation and target penetration capabilities from conical shaped charges with liner geometry of five types: (1) cone, (2) round-tipped cone, (3) hemisphere, (4) ellipsoid, and (5) trumpet, have been simulated via LS-DYNA Multi-Materials Arbitrary Lagrangian Eulerian (MMALE) technique. The objective is to observe the influences of liner types on the penetration features in target block while the amount of explosive and liner material are identical in all charge cases. Simulation results show that the hemispherical liner brings out the lowest penetration, while the ellipsoid and trumpet liners are of middle performance, but, the cone and round-tipped cone liners exhibit best penetration. Shaped charges with ellipsoid liner and trumpet liner present no remarkable discrepancy on penetration depth, however, the entrance holes are dramatically different in geometrical shape. Such penetration features are anticipated to be useful in technical design of shaped charges for some specific applications.

Numerical Analysis of the Formation of Shaped-Charge Jets from Charges with Conical and Semi-Spherical Liners of Variable Thickness

Studies of shaped charges with hemispherical liners of degressive thickness (decreasing from the top to the base) were continued based on numerical simulation. The possibility of increasing not only the velocity but also the mass of the head elements of shaped-charge jets to the level provided by conical liners of progressive thickness were analyzed. For this purpose, liners of degressive thickness in the form of a truncated sphere and a semi-ellipsoid slightly elongated along the charge axis were additionally studied.

On the Penetrability of Shaped Charges with Conical and Hemispherical Liners

On the Penetrability of Shaped Charges with Conical and Hemispherical Liners

Сравнительный анализ формирования кумулятивных струй из конических и полусферических облицовок

Сравнительный анализ формирования кумулятивных струй из конических и полусферических облицовок

О реализации принципа имплозии в кумулятивных зарядах с полусферическими облицовками дегрессивной толщины

О реализации принципа имплозии в кумулятивных зарядах с полусферическими облицовками дегрессивной толщины

Numerical simulation of the formation of shaped-charge jets from hemispherical liners of degressive thickness

The formation of shaped-charge jets from hemispherical copper liners of degressive thickness (decreasing from apex to bottom) is analyzed by numerical simulation of a twodimensional axisymmetric problem of continuum mechanics. The comparison was based on the parameters of the jet formed from a modern standard shaped charge with a conical liner which provides penetration of a steel target to a depth equal to 10 charge diameters. The comparative analysis was performed using calculated mass–velocity distributions and the ultimate jet length–velocity distributions obtained on their basis, from which the potential penetrability of jets was evaluated. It is shown that the shaped-charge jets formed by hemispherical shaped-charge liners of degressive thickness are comparable in head velocity and penetrability to the jets from conical liners.

Numerical Simulation of the Formation of Shaped-Charge Jets from Hemispherical Liners of Degressive Thickness

Numerical Simulation of the Formation of Shaped-Charge Jets from Hemispherical Liners of Degressive Thickness

Numerical analysis of the effect of the geometric parameters of a combined shaped-charge liner on the mass and velocity of explosively formed compact elements

The formation of high-velocity compact elements of shaped charges with a liner of a combined hemisphere-cylinder shape has been analyzed by numerical simulations of a two-dimensional axisymmetric problem of continuum mechanics. The influence of the radius and thickness of the hemispherical portion of the combined liner on the parameters of the compact elements has been studied. It is shown that in implosion of hemispherical liners whose thickness decreases from top to bottom, there is an increase in the velocity of the resulting jet flow. When using a hemispherical portion of variable thickness (to increase the velocity of the compact elements formed), it is necessary to solve two additional problems—to implement timely separation of the head part of the jet flow with increased velocity and increase its mass. For this, it is proposed to use the jet-forming part of the combined liner in the form of a truncated sphere or a slightly elongated ellipsoid of revolution. Combined shaped-charge liners in the form of a truncated ellipsoid of variable thickness were developed, allowing the formation of compact elements having a velocity of 7.5–10 km/s.

Explosive with metal lined cavities

The jet formation by hemispherical and trumpet liners have been explained by a simple extension of the hydrodynamic theory of jet formation by conical liners. The various phenomenon relating to jet formation and penetration have been correlated. The modified theory of penetration provides an accurate description of the variation of depth, velocity and time of penetration with stand off and nature of target material.

Wear patterns of, and wear volume formulae for, hemispherical acetabular cup liners

This study analyzed wear patterns of, and wear volume formulae for, hemispherical acetabular cup liners used in total hip replacement. The geometric patterns of the wear surface were first classified, then wear volume formulae were derived by integral calculus. Based on the theoretical maximal and minimal wear volumes, three-dimensional wear models constructed using SolidWorks® software or published formulae were used to verify the accuracy of the formulae proposed in this study. Analytical results showed that, with the exception of the pattern of a wear angle of 90°, hemispherical liner wear can be divided into two patterns. Once the wear pattern is determined from the wear angle and depth, a wear formula is applied to calculate the wear volume. The formulae and wear patterns described herein are crucial for more accurate performance evaluation of existing hip components implanted in patients, as well as for designing new hip components.

Liner dome shape effect on the annulus flow characteristics with and without swirl for a can-combustor model

The annulus flow characteristics of a can-combustor model for different liner dome shapes have been experimentally established under isothermal flow conditions for both nonswirling and swirling flows. Pressure taps were used to measure the wall pressure along the air casing and liner, whereas, velocity and pressure profiles were measured with the help of a threehole pressure probe in null mode. Turbulence intensity has also been measured with a constant temperature hot-wire anemometer. The effects of dome shapes on the recirculation zone, as well as on flow uniformity in the annulus region, for fixed dump gap, have been specially looked into. It was observed that the liner dome shape affects the size of recirculation zone and flow uniformity in the annulus region. The performance of the system was also assessed in terms of total pressure loss and static pressure recovery between the first and last measurement stations. It was found that swirling flow with a hemispherical dome liner gives better flow characteristics in the annulus region when compared with the other two dome shapes (namely, ellipsoidal, and vertical ellipsoidal).

Characteristics of Shaped Charges with Hemispherical Liners

AbstractDuring the last 10 years shaped charges with spherical liners have arosed great interest in research and development because their application in special munition results in an increase of performance. The present report presents measured characteristics of shaped charges with hemispherical liners. A short explanation of the jet formation process and the typical jet characteristics as a function of charge geometries are given, and the effect of liner materials is described. Additionally, the influence of various explosives and wave shapers have been studied. The important feature of such shaped charges is that the projectiles are associated with a high terminal ballistic effective part of the liner mass, which is of particular interest for application.

The Behavior of Shaped Charges with open‐poled hemispherical liners

AbstractThis paper discusses the effect of an opening at the pole of a hemispherical shaped‐charge liner. An experimental study was performed in which various diameter holes were made in otherwise similar shaped‐charge liners. Flash radiographs were taken to observe changes in the liner collapse and the jet characteristics. The collapse process and jet characteristics of a hemispherical liner are significantly altered for a hole diameter which is 10% or more of the outer liner diameter. The jet tip velocity is increased by 26% for a hole diameter‐to‐liner diameter ratio of 0.25. Explanations are presented for the behavior of the tip region of the shaped‐charge jet.

Explosive loading of lead hemispherical liners

This paper documents results of a combined analytical/experimental program to study the behavior of lead hemispheres of various thicknesses subjected to explosive shock loading. Previous studies of collapse and jetting of lead structures indicated that, due to the low melting temperature of lead, significant amounts of vapor were present in the jet. However, its high density, ready availability and low cost make lead an attractive material for industrial and military applications. Hemispherical lead liners of three different thicknesses were fabricated into aluminum confined cavity charges using OCTOL high explosive to drive the liners. Analysis of flash radiographs of the formation and jetting process indicated a gradual transition from an apparent liquid-vapor jet for the smallest wall thickness to a liquid-solid jet for the largest thickness. This apparent phase transition of the lead liners through a region of decreasing vapor lead to an analysis of the phenomena with the two-dimensional HULL code, a finite-difference Eulerian code for computations of hydrodynamic and elastic-plastic phenomena. Good correlation (8%) was obtained between experimentally determined and computed jet characteristics, thus permitting inferences to be drawn regarding the effects of material properties and strain rates on the response of lead to shock loading. Additional computations were made with HULL for copper hemispherical liners (for which more extensive experimental data was available) and these were compared with results from HELP, another Eulerian code. The EPIC code was also used to predict the geometric characteristics and velocities of the jets from the lead liners. On the whole, good agreement with experiments was obtained from all codes indicating that existing two- and three-dimensional codes may be valuable tools for the study of explosive forming problems. In addition, the temperature profiles of the jets from the lead liners are in general agreement with the quality of the flash radiographs (i.e. appearance of vapor) and with experimental measurements of the jet surface temperature.